In the semiconductor device manufacturing industry, device manufacturers have managed to transition to more closely toleranced process and materials specifications by relying on process tool manufacturers to design better and/or faster process and hardware configurations. However, as device geometries shrink to the nanometer scale, complexity in manufacturing processes increases, and process and material specifications become more difficult to meet.
A typical process tool used in current semiconductor manufacturing can be described by a set of several thousand process variables. The variables are generally related to physical parameters of the manufacturing process and/or tools used in the manufacturing process. In some cases, of these several thousand variables, several hundred variables will be dynamic (e.g., changing in time during the manufacturing process or between manufacturing processes). The dynamic variables, for example, gas flow, gas pressure, delivered power, current, voltage, and temperature can all change based on, for example, a specific processing recipe, the particular step or series of steps in the overall sequence of processing steps, errors and faults that occur during the manufacturing process, or changes in parameter values based on use of a particular tool or chamber (e.g., referred to as “drift”).
One way to monitor the manufacturing process is to specify a set of output values that defines the ideal values of parameters occurring during the manufacturing process. The actual output values of the manufacturing process are then compared to the ideal output values to determine if the actual output values are consistent with the ideal output values. This comparison is often performed manually by a process engineer to determine whether the particular output (e.g., processed semiconductor wafers) have desirable properties.
Generally, the process engineer specifies time trajectories of important process variables of the process tool that will be used during the processing. The specification of time trajectories is typically based on inspection of batches by the process engineer and a determination of acceptable time trajectories of variable values based on the output of the process tool and the experience of the process engineer. After a particular process tool undergoes preventive or periodic maintenance or after the passage of time, the values for acceptable variables can change. Such changes generally involve the process engineer manually re-specifying the acceptable time trajectories of process variables for the particular tool, e.g., to re-create or re-enter the specification.
Creating a specification in this manner is a lengthy and labor-intensive process, sometimes taking up to 20 hours or more. Additionally, this creation calls upon the expertise or experience of a process engineer, which can lead to a certain percentage of process faults based on human error or inconsistency in acceptable parameters between maintenance operations. Moreover, updating a specification, as part of a periodic maintenance plan and/or in response to changes within the particular process tool, involves a similar labor-intensive process. Updating the specification takes approximately the same amount of time and effort as creating a specification for the first time.